Only output includes once after the start of 'generate-time' when debugging.

During configure-time, GetIncludeDirectories may be called too, for example
if using the export() command. As the content can be different, it should
be output each time then.
Specify the target whose includes are being listed.
Merge topic 'clean-include-dirs-debugging' into next

db2fb69 Specify the target whose includes are being listed.
563b24c Only output includes once after the start of 'generate-time' when debugging.